Particularly geographical, historical, folkloric or linguistic connections.
I certainly can't find any such location on the map although there are a few coastal towns in Ulster that begin with "Bally", an alternate spelling. Ballycastle, for instance, seems to be associated with a legendary duel in which Congal, heir to the Kingdom of Ireland killed the King of Norway.
However, according to A Dictionary of Derivations, Sullivan, Robert (1860) p.283, the term is included in the names of at least 2000 Irish locations. From an etymological standpoint the word seems simply to mean a "place" or "settlement".
Part of the reason I ask is that Yeats is a poet of the first order so I tend not to assume anything is random. His plays are interesting, in part, because they occupy a place similar to the work of great Athenian dramatists, who commented on the great mythical cycles of their cultures, recorded centuries earlier by their forbearers.